Liquid fuel pumps for internal combustion engines



Sept. 1, 1959 K, A. W, KEMP 2,902,017

LIQUID FUEL PUMPS FOR INTERNAL COMBUSTION ENGINES Filed Sept. 4, 1957 l 2,902,017 Patented Sept. 1, 1959 LIQUID FUEL PUMPS FOR INTERNAL COMBUSTION ENGINES KennethAlbert Walters Kemp, Ealing, London, England, asslgnor to C.A.V. Limited, London, England l Application September 4, 1957, Serial No. 682,064

Claims priority, application Great Britain September 7, 1956 2 Claims. (Cl. 123-139) This invention relates to liquid fuel pumps for internal combustion engines, of the kind comprising a feed pump, an injection pump, an adjustable throttle for controlling the rate of supply of fuel from the feed pump to the injection pump, and a distributor for conveying discharges from the injection pump to each in turn of the engine cylinders.

An inherent disadvantage of pumps of the kind aforesaid is that the instant at which each discharge to the engine is initiated may vary with the rate of supply of fuel from the feed to the injection pump, a diminished rate being accompanied by a delay of the commencement of the discharge.

The primary object of the present invention is to provide a pump of the aforesaid kind, in a form which ensures that the discharge from the injection pump shall be initiated at a definite instant in each cycle of action of v the pump irrespective of the quantity of fuel discharged in each cycle.

When the speed of the engine is variable yover a wide range, it is also desirable that the instant of discharge from the injection pump shall be advanced with increase of speed, and a further object of the present invention is to enable this requirement to be met in a convenient manner.

A pump of the kind aforesaid in accordance with the invention has combined with it anadjustable cam for actuating Vthe injection pumpfa spring for automatically advancing thercam relatively to and after each discharge action of the injection pump, and a dash pot for ccntrolling the action of the spring.

Also the invention comprises a pump as specified in the preceding paragraph, in which the means for adjusting the cam is movably contained Within an enclosing cylin` der which is slidable in opposite directions under the opposed actions of a spring and pressure of liquid fuel supplied by the feed pump.

In the accompanying drawings:

Figure l is a sectional side elevation of one form of combined feed and injection pump of the kind for which the present invention is required.

Figure 2 is a sectional end -view of the injection pump taken on the line 2-2 of Figure l and illustrating one embodiment of the invention.

Figures 3 and 4 are respectively similar views to Figure 2 illustrating other embodiments of the invention.

Referring to Figure 1, the pump there shown is provided with a body part a which at one end contains a feed pump of the kind comprising a rotary impeller b provided with vanes. Fuel is conveyed to this pump through an inlet passage c and is discharged to a passage d which latter may be connected to the inlet passage by a relief valve e loaded by a spring which limits the pressure which can be generated by this pump. At the other end of the body part is contained the fuel injection pump. This comprises a rotary body part g having a transverse bore h (Figure 2) containing a pair of reciprocatory plungers i which (through rollers k at their outer ends) co-operate with a surrounding annular cam mv. 'Ihe rotary parts of the feed and injection pumps are interconnected by a spindle n which has formed in it an axial passage 0 and radial passages p, q, and which serves as a distributor. The spindle n is driven by the engine through a shaft r. The arrangement is such that liquid fuel from the feed pump is discharged along the passage d in the body part and through a manually adjustable throttle s and passage t to radial ports p in the spindle and thence to the injection pump. During inward movements of the plungers of the injection pump under the action of the cam, fuel is discharged along the passage o and through the other radial port q in the spindle to each in turn of passages u lea-ding to the different cylinders of the engine. It will be understood that the radial ports p and q are so `disposed that when any one of the ports p is open to the passage t the port q is closed, and when the port q is open to any of the passages u the ports p are all closed.

In the embodiment of the invention shown in Figure 2, the annular cam m is mounted in the body part with angular freedom of movement and from one side of the cam extends a short arm v which at its outer end occupies a gap w in a reciprocable plunger x contained in a cylinder y which is closed at both ends and which is incorporated -With the body part of the pump. In one end of this cylinder is contained a spring 5 which urges the plunger in the direction for imparting to the cam an angular movement in the direction which is opposite to the direction of rotation of the injection pump, which latter direction is indicated by the arrow in Figure 2. The ends of the cylinder, the gap in the plunger, and the interior of the cam are filled with oil of any convenient viscosity, which may be the fuel itself. Also the end of the plunger on which the spring acts has formed in it a narrow groove 6 in communication with the gap into which the said arm extends. Further a bore 7 is formed in the arm through which the oil can flow between the said gap and the cam. Another narrow groove 8 is also formed in the plunger between the gap and the other end of the cylinder. By virtue of the grooves 6 and 8 the plunger x forms with the cylinder y a dash pot for controlling the effect of the spring 5 on the plunger.

The arrangement is such that after each `discharge action of the injection pump, the spring 5 advances the cam at a rate controlled by the dash pot above mentioned. As soon as the rollers k of the pump plungers encounter lobes on the cam these plungers impart an opposite movement to the cam against the action of the spring at a rate determined by the dash pot action. During this phase the interaction of the cam and rollers causes the injection pump to effect the next discharge, the cam being advanced by the spring during each interval between successive discharges. When the fuel is fed to the injection pump at a low rate, the injection pump plungers i are moved outwardly to a smaller extent than when the fuel is fed to the injection pump at a higher rate, and the rollers [c on the outer ends of these plungers subsequently encounter higher parts of the cam lobes than would be the case if the plungers were moved outwardly to a greater extent. This would result in variation of the instant of commencement of discharge of the injection pump were it not for the fact that the cam m is advanced by the action of the spring 5 on the dash-pot plunger x through a greater angular distance than when fuel is fed to the injection pump at a high rate, this greater advance of the cam being permitted by reason of the fact that the advance continues until the rollers k on the injection pump plungers encounter the higher parts of the cam lobes. By suitably correlating the action of the spring and -dash pot, the instant of commencement of discharge of the injection pump can be made substantiab ly constant and independent of the rate of supply ofY fuel to the injection pinnp.

To enable the instant at which each discharge of the injection pump is initiated, to be varied with change of speed of the engine, the plunger x is contained in a cylinder 9 Which is slidable in the cylinder y as shown in Figure 3. At one end the cylinder y is supplied with fuel oil from the feed pump through a passage 10 connected to the passage d of Figure l, and this end of the cylinder y communicates with the adjacenty end of the cylinder 9'tl1rough a restricted orifice 11. The other end of the cylinder y contains a spring 12 acting on the slidable cylinder and is in communication with the interior of Vthe cam by way of a passage 13 and the above described gap w in the plunger x and the bore 7 in the arm v so that the oil with iwhich the interior of the cam is lled can How into and out of the last mentioned end of the cylinder y during movements `of the slidable cylinder 9; The end of the slidable cylinder containing the spring communicates with the-other end of this cylinder through a passage 14 formed in the plunger x. The end of the passage 14- adjacent the last mentioned end =of the slidable cylinder is restricted as shown so that this passage enables the plunger x to form with the slidable cylinder a dash pot.

The arrangement is such that with a given load or speed condition associated with the engine, the plunger x contained in the slidable cylinder 9 acts on the cam in the manner above described with reference to Figure 2, but with a varying feed pump ydelivery pressure dependent on the speed of the engine, the slidable cylinder moves in response to the opposed actions of the fuel pressure and spring 12, and thereby varies the instant at which the rollers k on the injection pump plungers z' encounter the lobes on the cam m. With increase of speed the instant at which each discharge from the injection pump is initiated is progressively advanced.

Referring to Figure 4, the construction thereshown is essentially similar to that of Figure 3, but diiers in that the restricted orifice 11 in the cylinder 9 is omitted, and at the two ends of the said cylinder are provided grooves 14, 15 through which dash pot liquid can ow to and from the gap w containing the arm v. Also the end of the cylinder y containing the spring 12 communicates with the adjacent end of the cylinder 9 by way of an aper- 45 ture 16.

Having thus described my invention what I claim ,as new and desire to secure by Letters Patent is:

l. Means for supplying liquid fuel to a multi-cylinder internal combustion engine, comprising in combination a feed pump, a rotary injectionpump, an adjustable throttle for controlling the rate of supply of liquid fuel from the feed pump -to the injectionpump, a rotary distributor for conveying successiveY discharges from the injection pump to the engine cylinders in turn, an adjustable cam for effecting discharge of the injection pump, a cam-adjusting plunger having an operative connection with the cam, a cylinder in which the plunger is movable, and which forms with the plunger a dash pot, and a spring mounted in one end' of the cylinder and acting on the corresponding end of the plunger to move the latter under the control of the dash pot in a direction opposite to the direction of rotation of the injection pump, and thereby automatically advancing the cam relatively to and after each ldischarge action of the injection pump.

2. Means for supplying liquid fuel to a multi-cylinder internaly combustion engine, comprising in combination a feed pump, an injection pump, an adjustable throttle for controlling the rate of supply of liquid fuel from the feed pump to the injection pump, a rotary `distributor for conveying successive discharges from the injection pump to the engine cylinders in turn, an adjustable cam for effecting discharge of the injection pump, a cam-adjusting plunger having an operative connection with the cam, a cylinder in which the plunger is movable, and which forms with the plunger a dash-pot, a spring mountedV in one en'd of the cylinder and acting on the corresponding end of the plunger for moving the latter under the control of the dash-pot, and thereby automatically advancing the cam relative to and after each discharge action of the injection pump, a second cylinder in which the dash-pot cylinder is slidably mounted, a second spring acting ion the end of the dash-pot cylinder remote the rst mentioned spring, and means for subjecting the opposite end of the dash-pot cylinder to the delivery pressure of the feed pump, so that the position of the dash-pot cylinder varies with the delivery pressure of the feed pump, and thereby causes the plunger in the dash-pot cylinder to vary the position of the cam.

References Cited in the le of this patent UNITED STATES PATENTS 

